During the last year we have obtained convincing biochemical evidence that coated vesicles transport membrane glycoproteins from endoplasmic reticulum to plasma membrane, and also transport epidermal growth factor (EGF) a polypeptide hormone which associates with fibroblast membrane receptors, from the plasma membrane to the lysosome. These studies demonstrated that VSV G proteins and EGF can be shown by biochemical and immunochemical means to be associated with coated vesicles. The kinetics of both associations demonstrate the coated vesicles' transport function. We have begun to investigate the possibility that coated vesicles carry acetylcholine receptors and procollagen from one membrane in the cell to another. We also hope to investigate the mechanism of formation and fusion of coated vesicles using various drugs which are proposed to block these processes.